Sanitary waste storage devices found in recreational vehicles, travel trailers, camping structures, boats, and other portable toilet facilities, such as commonly found at camp grounds, construction sites, temporary bathroom facilities for large public gatherings, like sporting events, natural disaster points, etc., comprise sanitary waste water systems and tanks for the capture, retention and containment of human waste matter until such time as it can be transported to a central “dumping station”. Typically, at the dumping station the waste matter is piped to a sewage treatment system. While solid and liquid waste matter is held, they will naturally degrade in a limited fashion aerobically, but quickly degrade anaerobically due to high soil levels within the waste water tank, and due to the low levels of aeration in such tanks compared to open pipe systems.
A further significant factor in the degradation process, and the resulting developing odors in portable waste storage systems is the concentration of waste compounds stored in holding tanks is often much greater than in sanitary waste systems found in homes and city sewage systems. This is often due to the limited use of water in portable sanitary systems. In comparison, home sewage systems routinely operate with much more water content, which allows for greater aeration in transmission throughout sewerlines. In addition, mean summer time temperatures accelerate degradation in waste tanks exposed to open, ambient air temperatures, where temperatures can average more than 30° C.
Especially under anaerobic conditions, degradation of waste matter becomes exacerbated by the foregoing factors resulting in the rapid discharge of noxious odors/fumes. The prevention or limiting of these noxious odors/fumes is vital to the performance and effectiveness of additives in deodorizing waste water. At a certain point in the normal degradation of waste, odor emission becomes unacceptable for normal occupation of temporary and/or portable structures where the waste water tanks are stationed.
While most waste water tank deodorizing compositions appear to provide some level of inhibition, retardation and/or masking of odor build-up due to the generation of hydrogen sulfide gas in the process, their performance has not been readily determinable by objective comparative testing protocols. Consequently, measurable and reliable performance standards of waste water tank deodorizer products have been limited principally to less reliable subjective evaluation standards.
A waste water holding tank is commonly expected to hold waste compounds for five days. The traditional method of controlling odor during this five day holding period has been through the use of formalin solutions. The conventional wisdom has been to include 400-600 ppm formaldehyde at peak tank capacity. The art has expanded in the use of less hazardous materials than formaldehyde, but their introduction has been the result of much trial and error performance evaluation. Consequently, there has been very little verifiable data to prove efficacy, or basis for developing and optimizing performance, or for formulating better performing waste water tank deodorizers.
Standardized test methods to determine efficacy of a deodorizing compound are sparse in the art with the exception of the German Blue Angel Award Program number RAL-UZ 84a Award Criteria Annex 2 Test Method for determining the Serviceability of Sanitary Additives for Odor Control in Mobile Toilets dated February 2005. This method is quite difficult and expensive to perform due to its procedure and conditions that must be performed. The German Blue Angel Program requires 10 people to rate the odor subjectively on a level of disagreeability. Also, the Program is potentially an unsafe procedure because it requires the use of swine feces. Subjective personal preference as to disagreeability of odors would also be more preferably replaced with a more quantifiable objective method.
As pointed out above, state of the art methods have relied principally on deodorizer technologies comprising formalin solutions supplied at about 50-100% formalin or approximately 18-37% formaldehyde. Other antimicrobials that have been used as waste water tank deodorizers have included quaternary ammonium compounds such as BTC® series (a registered trademark of the Stepan Company Northfield, Ill.) and Bardac® or Barquat® (both a registered trademark of Lonza Inc, Allendale, N.J.); or other compounds such as Dowicil® (a registered trademark of The Dow Chemical Company of Midland, Mich.) or Bronopol® (2-bromo-2-nitropropane-1,3-diol). Some non-antimicrobial additives include various nitrate salts, and bacterial or enzyme suspensions.
However, there still remains an unfulfilled need for an accurate and reliable scientific method for objective testing and evaluating the performance of waste water tank deodorizers formulated with the goal of modifying, retarding or inhibiting the degradation of waste products and generation of odoriferous and potentially hazardous compounds, e.g., hydrogen sulfide gas.
Likewise, there is also a need for an adjunct synthetic/surrogate waste water composition that can perform as a standardized test media and substitute for biohazardous natural waste material currently used in testing and evaluating the performance of waste water tank deodorizers.